Magnetic field generator having a high frequency current lower layer coil and a resonance upper layer coil

ABSTRACT

A magnetic field generator includes: an upper layer resonance coil composed of a first conductive material and forming a loop circuit having a coil portion; a lower layer coil composed of a second conductive material and forming a loop circuit having a coil portion arranged opposite to the coil portion of the upper layer coil at a predetermined distance; and a substrate supporting the upper layer coil and the lower layer coil and having a dielectric material between the upper layer coil and the lower layer coil. A high-frequency current is supplied to the lower layer coil and a high-frequency current having a phase opposite to that of the high frequency current supplied to the lower layer coil flows through the upper layer coil. A length per loop of the coil portion in the upper layer coil and the coil portion in the lower layer coil is matched to one wavelength of the high-frequency current.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. Utilitypatent application Ser. No. 17/675,109 filed on Feb. 18, 2022, which isbased on and claims the benefit of priority of Japanese PatentApplication No. 2021-026889, filed on Feb. 23, 2021, the disclosures ofwhich are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure generally relates to a magnetic field generatorand a magnetic sensor including the magnetic field generator.

BACKGROUND

For comparison, a prior art discloses a loop gap resonator correspondingto a magnetic field generator that generates a high-frequency magneticfield in an axial direction of a coil. In the loop gap resonator, anelectric field of the same path is generated in the entirecircumferential direction of the loop-shaped electrode, in other words,the cylindrical shape electrode. That is, a magnetic field is generatedin a path that extends from an inside of the cylinder formed by theelectrode to an outside of the cylinder at one end of the cylinder inthe axial direction, and the magnetic field is further guided to another end of the cylinder along an outer peripheral surface of thecylinder, and the magnetic field returns to the inside of the cylinder.Therefore, a high-frequency magnetic field is generated in the axialdirection of the coil, passing through the inside of the cylindricalcoil formed by the electrode.

It is desired to detect a very small external magnetic field, thus it isnecessary to bring the source of the magnetic field and the magneticsensor closer to each other. If the sensor is a cylindrical loop gapresonator, it is necessary to bring a detection target closer to aninside of the cylinder. However, since there are loop coils, resonators,and a substrate on which they are disposed on the XY plane, there may bea certain limit of how much the resonator, i.e., the cylinder, and thedetection target can be brought close to each other.

On the other hand, if the source of the external magnetic field isplaced directly above or below the cylinder-shape magnetic fieldgenerator, that is, at one of the two proximate positions in the axialdirection, the distance between the two becomes short, but the externalmagnetic field cannot be measured because the loop gap resonator has nosensitivity in the axial direction. In order to create sensitivity inthe axial direction, it is necessary to generate a high-frequencymagnetic field in the XY plane.

SUMMARY

It is an object of the present disclosure to provide a magnetic fieldgenerator capable of generating a high-frequency magnetic field in an XYplane, when an axial direction of a coil is set as a Z axis, and a planeperpendicular to the Z axis is set as an XY plane, and to also provide amagnetic sensor having such a magnetic field generator.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an overall configuration diagram of a magnetic sensor providedwith a magnetic field generator according to a first embodiment;

FIG. 2 is a diagram showing a cross-sectional view taken along a lineII-II of FIG. 1 ;

FIG. 3 is a diagram showing the magnetic field generator extracted fromFIG. 1 ;

FIG. 4A is a diagram showing a relationship between a physical lengthand an electric length of a wiring of a loop circuit when a dielectricconstant of a substrate is same;

FIG. 4B is a diagram showing a relationship between the dielectricconstant and the electric length of the substrate when the physicallength of the wiring of the loop circuit is the same;

FIG. 5A is a perspective view illustrating a magnetic field generated ina lower layer coil;

FIG. 5B is a perspective view illustrating a magnetic field generated inthe lower layer coil and an upper layer coil and a high-frequencymagnetic field generated thereby;

FIG. 6 is a cross-sectional view illustrating a magnetic field generatedin the lower layer coil and the upper layer coil and the high-frequencymagnetic field generated thereby;

FIG. 7 is a waveform diagram of a high-frequency current;

FIG. 8 is a cross-sectional view illustrating a high-frequency magneticfield generated by a winding coil wound by a plurality of times as acomparative example;

FIG. 9A is a diagram showing directions of electric currents flowingthrough the upper layer coil and the lower layer coil by simulation witharrows;

FIG. 9B is an enlarged view of a IXB region in FIG. 9A;

FIG. 9C is an enlarged view of a IXC region in FIG. 9A;

FIG. 10 is a diagram showing a simulation result of a high-frequencymagnetic field generated by the magnetic field generator;

FIG. 11 is a diagram showing the magnetic field generator provided inthe magnetic sensor according to a second embodiment;

FIG. 12 is a cross-sectional view illustrating a magnetic fieldgenerated in a lower layer coil and an upper layer coil and ahigh-frequency magnetic field generated thereby in a XII-XII crosssection in FIG. 11 ;

FIG. 13 is a diagram showing a magnetic field generator provided in themagnetic sensor according to a third embodiment;

FIG. 14 is a cross-sectional view taken along a XIV-XIV line in FIG. 13;

FIG. 15 is a diagram showing a magnetic field generator provided in themagnetic sensor according to a fourth embodiment;

FIG. 16 is a cross-sectional view taken along a XVI-XVI line in FIG. 15;

FIG. 17 is a diagram showing a magnetic field generator provided in themagnetic sensor according to a fifth embodiment;

FIG. 18 is an illustration of various positions between a first leadportion and a second lead portion in the upper layer coil as points G toK;

FIG. 19A is a diagram showing a relationship between a standing wave ofa high-frequency current and points G to K in FIG. 18 ;

FIG. 19B is a diagram showing a relationship between the standing waveof a high-frequency current and points G to K in FIG. 18 ;

FIG. 20A is a diagram showing a state in which a magnetic fielddirection is clockwise in a sixth embodiment;

FIG. 20B is a diagram showing a state in which the magnetic fielddirection is counter-clockwise in the sixth embodiment;

FIG. 21 is an overall configuration diagram of the magnetic sensorprovided with the magnetic field generator according to a seventhembodiment;

FIG. 22 is a cross-sectional view taken along a XXII-XXII line of FIG.21 ;

FIG. 23 is a diagram showing the magnetic field generator extracted fromFIG. 21 ;

FIG. 24 is a diagram showing directions of electric currents flowingthrough the upper layer coil and the lower layer coil by simulation witharrows; and

FIG. 25 is a diagram showing a simulation result of a high-frequencymagnetic field generated by the magnetic field generator.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be describedwith reference to the drawings. In the following embodiments, the sameor equivalent parts are denoted by the same reference signs.

First Embodiment

The following describes a first embodiment. In the present embodiment, amagnetic sensor provided with a magnetic field generator is described.The magnetic sensor measures, i.e., detects, an external magnetic fieldbased on a high-frequency magnetic field generated by the magnetic fieldgenerator. As shown in FIG. 1 , the magnetic sensor is configured toinclude a diamond 2, a light source 3, a temperature control unit 4, ameasurement unit 5, and the like in addition to a magnetic fieldgenerator 1.

As shown in FIGS. 1 to 3 , the magnetic field generator 1 is configuredby arranging two loop-shaped, upper layer coil 20 and lower layer coil30 on a substrate 10 in an overlapping, layered manner. In the drawing,an XY plane is a plane parallel to a surface (e.g., an upper surface) ofthe substrate 10, and a normal direction with respect to the XY plane isa direction parallel to the Z axis. Further, the magnetic fieldgenerator 1 is provided with an upper layer power source 40 which is amechanism for energizing the upper layer coil 20 and a lower layer powersource 50 which is a mechanism for energizing the lower layer coil 30.

The substrate 10 supports the upper layer coil 20 and the lower layercoil 30. For example, the substrate 10 is made of an epoxy-based resinmaterial or the like, and has a structure including the upper layer coil20 and the lower layer coil 30 inside. A dielectric composed of a partof the substrate 10 is sandwiched between the upper layer coil 20 andthe lower layer coil 30.

Here, the substrate 10 is provided as a multi-layer substrate, which hasthe upper layer coil 20 and the lower layer coil 30 built therein, bylayering and combining a plurality of printed circuit boards. Forexample, a plurality of printed circuit boards respectively having frontand back surfaces covered with a metal foil such as copper foil areprepared, some of which are patterned by etching to form the upper layercoil 20, the lower layer coil 30 and the like. Then, the printed circuitboards after patterning are combined/integrated by press processing orthe like to form the substrate 10 which has the upper layer coil 20 andthe lower layer coil 30 built therein.

Further, as shown in FIGS. 1 to 3 , the substrate 10 is formed with athrough hole 11 piercing through an inside of the upper layer coil 20and the lower layer coil 30. The through hole 11 may be formed so as topenetrate the front and back surfaces of the substrate 10, which in thiscase has a cylindrical shape. The diamond 2 and the temperature controlunit 4, which is described later, are arranged in the through hole 11.

Note that, although omitted in FIGS. 1 and 3 , the upper layer coil 20and the lower layer coil 30 are, as shown in FIG. 2 , sandwiched betweenthe front and back surfaces of the substrate 10 and an upper GND layer12 and a lower GND layer 13 having a ground potential are symmetricallyarranged (hereinafter “ground” may be designated as GND). In suchmanner, a microstrip line is configured by arranging the upper GND layer12 and the lower GND layer 13 vertically symmetrically on the substrate10. The upper GND layer 12 and the lower GND layer 13 are formed tocover at least a coil portion 21 of the upper layer coil 20 and a coilportion 31 of the lower layer coil 30. Then, the upper GND layer 12 ispartially removed, for example, at a position outside the coil portion21 and the coil portion 31, and, via the removed portion, an electricalconnection between the upper layer power source 40 and the upper layercoil 20 and an electrical connection between the lower layer powersource 50 and the lower layer coil 30 are respectively enabled. Further,the through hole 11 is formed to penetrate the upper GND layer 12 andthe lower GND layer 13.

The upper layer coil 20 has the coil portion 21, a slit 22 thatpartially cuts out the coil portion 21, and a lead portion 23 that isarranged on both sides of the slit 22 and is drawn out in an outerperipheral direction of the coil portion 21. The coil portion 21 and thelead portion 23 are made of a first conductive material, such as copperor the like as described above, for example.

The coil portion 21 constitutes a loop circuit composed of a loop-shapedcoil. Specifically, the coil portion 21 has an annular shape having apredetermined width, and the length per loop, that is, an electriclength of one loop, is set to one wavelength of the high-frequencycurrent flowing from the upper layer power source 40. That is, adistributed constant circuit is configured such that one wavelength ofthe high-frequency current and the electric length are set to be aboutthe same. When a high-frequency current near 2.87 GHz is used, onewavelength is approximately 100 mm. Therefore, the radius of the coilportion 21 is approximately 16 mm.

However, since a wavelength shortening rate changes according to thematerial around the coil, that is, the dielectric constant of thesubstrate 10, the electric length per loop of the coil portion 21 can beset according to the wavelength shortening rate. For example, when FR4composed of glass epoxy is used as an epoxy-based resin material, thedielectric constant is about 4, which makes the radius about 8 mm due tothe wavelength shortening rate, and the length of one loop of the coilportion 21 is set to be approximately 50 mm.

Generally, the relationship between the physical length and the electriclength of the wiring of the loop circuit when the dielectric constant ofthe substrate is same is shown in FIG. 4A. In FIG. 4A, L means areference length, and 1 L, 2 L, 5 L, and 10 L mean a length obtained bymultiplying the reference length by a numerical magnification. Further,the relationship between the dielectric constant and the electric lengthof the substrate when the physical length of the wiring of the loopcircuit is same is shown in FIG. 4B. In FIG. 4B, εr means a relativepermittivity, εr: 1, εr: 2, εr: 5, εr: 10, and εr: 20 mean numericalvalues of the relative permittivity. As shown in these drawings, theelectric length in the loop is proportional to the physical length, andthe higher the dielectric constant, the longer the electric length.Therefore, in the present embodiment, the electric length per loop ofthe coil portion 21 composed of the loop coil is set based on thephysical length of the upper layer coil 20 corresponding to the wiringand the relative permittivity of the substrate 10.

The length of one loop of the coil portion 21 and one wavelength of thehigh-frequency current do not have to completely match. That is, if theXY plane can be oriented in the magnetic field direction as describedlater in generating the high-frequency magnetic field, the length of oneloop of the coil portion 21 and one wavelength of the high-frequencycurrent may be different from each other. For example, a magnetic fieldis generated on the XY plane even if a deviation of ±20% occurs, but itmay preferably be within ±10%. Further, the through hole 11 describedabove has a dimension corresponding to the dimension of the coil portion21, and, if the radius of the coil portion 21 is approximately 16 mm,the radius is set to be less than that.

The slit 22 is a gap provided between one end and the other end of thecoil portion 21, which may be several of one tenth mm to several mm, forexample, and the length of one loop of the coil portion 21 excludingsuch gap is set to be the wavelength of a high-frequency current.

The lead portion 23 has a first lead portion 23 a and a second leadportion 23 b drawn from one end of the coil portion 21, and the firstlead portion 23 a is connected to the upper layer power source 40, andthe second lead portion 23 b is connected to the GND. As a result, apath of electric current is formed in which the electric current flowingfrom the upper layer power source 40 flows from the first lead portion23 a to the second lead portion 23 b through the coil portion 21.Further, in order to suppress a reflection of the electric currentflowing from the second lead portion 23 b to the GND, a resistor 60 isprovided at a position between the second lead portion 23 b and the GND.

The lower layer coil 30 has a shape corresponding to the upper layercoil 20. The lower layer coil 30 also has the coil portion 31, a slit 32that partially cuts out the coil portion 31, and a lead portion 33 thatis arranged on both sides of the slit 32 and is drawn out/extends in theouter peripheral direction of the coil portion 31. The coil portion 31and the lead portion 33 are made of a second conductive material, suchas copper or the like as described above, for example.

The coil portion 31 constitutes a loop circuit composed of a loop-shapedcoil. Specifically, the coil portion 31 is formed in the same shape anddimensions as the coil portion 21 of the upper layer coil 20, and isarranged to face the coil portion 21 at a predetermined distance.

The slit 32 also has the same dimensions as the slit 22 of the upperlayer coil 20. In the present embodiment, the slit 32 is formed at thesame position as the slit 22.

The lead portion 33 has a first lead portion 33 a and a second leadportion 33 b drawn from one end of the coil portion 31, and the firstlead portion 33 a is connected to the lower layer power source 50, andthe second lead portion 33 b is connected to the GND. In such manner, apath of electric current is formed in which the electric current flowingfrom the lower layer power source 50 flows from the first lead portion33 a to the second lead portion 33 b via the coil portion 31. Further,in order to suppress a reflection of the electric current flowing fromthe second lead portion 33 b to the GND, a resistor 70 is provided at aposition between the second lead portion 33 b and the GND.

The center of the coil portion 21 of the upper layer coil 20 and thecenter of the coil portion 31 of the lower layer coil 30 arealigned/matched, and their central axes are the Z axis. The central axismay also be called as the coil central axis. Further, between the upperlayer coil 20 and the lower layer coil 30, one surface parallel to thecoil portion 21 and the coil portion 31 is the XY plane.

The upper layer power source 40 is a high-frequency power source thatsupplies a high-frequency current to the upper layer coil 20. The upperlayer power source 40 generates a high-frequency current in which onewavelength is the length of one loop of the coil portion 21. The lowerlayer power source 50 is a high-frequency power source that supplies ahigh-frequency current to the lower layer coil 30. The lower layer powersource 50 generates a high-frequency current in which one wavelength isthe length of one loop of the coil portion 31. Here, a high-frequencycurrent of about 2.87 GHz is passed from the upper layer power source 40and from the lower layer power source 50.

The magnetic field generator 1 is configured in the above-describedmanner. Although the details of the magnetic field generator 1configured in such manner are described later, a high-frequency magneticfield is generated in the XY plane which is positioned between the upperlayer coil 20 and the lower layer coil 30.

The diamond 2 corresponds to a magnetic field measuring element thatmeasures an external magnetic field, and is arranged in the through hole11. Here, the diamond 2 is arranged to be positioned in the XY planethat generates a high-frequency magnetic field at a position between theupper layer coil 20 and the lower layer coil 30. When the diamond 2 isirradiated with light having a specific wavelength and when ahigh-frequency magnetic field is applied thereto, the diamond 2undergoes wavelength conversion to generate fluorescence.

The light source 3 irradiates the diamond 2 with, for example, a laserbeam as light having a specific wavelength. The light source 3 isarranged outside of the substrate 10, that is, outside of the upperlayer coil 20 and the lower layer coil in the radial direction, andirradiates the diamond 2 with light through a space between the upperlayer coil 20 and the lower layer coil. Here, for example, the lightsource 3 is arranged so that the laser light is irradiated along the XYplane. However, the light source 3 may also be arranged so that thelaser light is irradiated obliquely with respect to the XY plane. Forexample, a green laser beam is output from the light source 3, and thewavelength is converted by the diamond 2 to generate red fluorescence.

The temperature control unit 4 is used to adjust temperature of thediamond 2. The temperature control unit 4 is arranged to be in contactwith the diamond 2. The diamond 2 generates fluorescence by convertingthe wavelength of the irradiated light, and at such time, energy lossoccurs and heat is generated. The temperature control unit 4 adjuststemperature of the diamond 2 at the time of heat generation by coolingthe diamond 2 or by other method.

The measurement unit 5 is for measuring the light emitted by the diamond2, and is composed of a light receiving element or the like. Asdescribed above, when the diamond 2 fluoresces, fluorescence is outputin various directions. Therefore, by arranging the measurement unit 5outside the through hole 11, the measurement unit 5 is enabled tomeasure the light emission of the diamond 2. Then, the measurement unit5 measures the light emitted by the diamond 2 to observe physicalphenomena such as a shape of the diamond 2 and the like. Since thediamond 2 absorbs the energy due to the unpaired electrons of themeasurement target based on ESR (Electron Spin Resonance) and changesits characteristics, measurement of the generated minute magnetic fieldby the measurement target becomes measurable by/via the measurement ofphysical phenomena.

The magnetic sensor including the magnetic field generator 1 accordingto the present embodiment is configured in the above-described manner.As described above, the magnetic field generator 1 according to thepresent embodiment generates a high-frequency magnetic field, and thediamond 2 can be used as a measuring element to measure the externalmagnetic field. At such time, the magnetic field generator 1 isconfigured to generate a high-frequency magnetic field which has themagnetic field direction aligned in the XY plane, and in addition sincethe substrate 10 is thin, the minute amount of the magnetic fieldgenerated by the measurement target becomes measurable on the front andback surfaces above and below the substrate 10. Further, since thethrough hole 11 formed by hollowing out the substrate 10, themeasurement target that is the source of the minute magnetic field canbe brought closer to the diamond 2 or to the high-frequency magneticfield, thereby the minute magnetic field can be more accuratelymeasured.

Here, the mechanism by which the magnetic field direction of thehigh-frequency magnetic field can be set to the XY plane as describedabove is described in comparison to the conventional structure.

As described above, the magnetic field generator 1 of the presentembodiment has the upper layer coil 20 and the lower layer coil 30arranged in an overlapping manner, which respectively receive supply ofthe high-frequency current from the upper layer power source 40 and thelower layer power source 50. Further, the lead portion 23 of the upperlayer coil 20 and the lead portion 33 of the lower layer coil 30 arearranged to have the same position when viewed from the normal directionof the substrate 10. In such a configuration, a high-frequency currenthaving a phase difference of 180° is applied to the upper layer coil 20and the lower layer coil 30. Then, the frequency of the high-frequencycurrent is set to around 2.87 GHz so that one wavelength of thehigh-frequency current becomes substantially equal to the length of oneloop of the coil portion 21 of the upper layer coil 20 and the coilportion 31 of the lower layer coil 30.

In the following description, the phase of the high-frequency current atan end (i.e., the lead portion) of the coil portion 21 of the upperlayer coil 20 and the coil portion 31 of the lower layer coil 30 wherethe high-frequency current is input at a supply start timing of thehigh-frequency current is referred to as an initial phase.

When such a high-frequency current is passed, for example, in the lowerlayer coil 30, as shown in FIGS. 5A and 5B, a high-frequency current ispassed (i.e., flows) from the first lead portion 33 a to the second leadportion 33 b. In such case, at a point P1, which is a position of thefirst lead portion 33 a, of 0° and a point P2, which is a position ofthe second lead portion 33 b, of 360°, the polarity of the electriccurrent is reversed from each other at point symmetric position aboutthe coil central axis. For example, assuming that the waveform of thehigh-frequency current flowing at each position from 0° to 360° at anarbitrary timing is as shown in FIG. 7 , the phases are reversed atpoints P3 and P4, and the directions of the electric currents becomeopposite to each other. Therefore, for example, at the point P3 at a 90°position and the point P4 at a 270° position in FIG. 5A,counter-clockwise magnetic fields E1 and E2 are generated based on theright-handed screw rule when seen from the first lead portion 33 a andthe second lead portion 33 b.

On the other hand, since a high-frequency current having a phasedifference of 180° from that of the lower layer coil 30 is passed to theupper layer coil 20, a magnetic field opposite to that of the lowerlayer coil 30 is generated in the upper layer coil 20. Therefore, forexample, when the magnetic fields at the positions of the points P3 andP4 are shown, the upper layer coil 20 has clockwise magnetic fields E3and E4 generated therein, and the lower layer coil 30 has acounter-clockwise magnetic fields E1 and E2 generated therein,respectively as shown in FIGS. 5B and 6 .

Therefore, directions of the magnetic fields E1 to E4 match (i.e., arealigned) with each other at/around the positions of the points P3 and P4in the substrate 10, or in other words, at positions in between theupper layer coil 20 and the lower layer coil 30, i.e., (A) the magneticfields E1 and E3 have the same direction at a lower part of an upperlayer portion having the upper layer coil 20 (i.e., at a position closeto the lower layer coil 30) and an upper part of a lower layer portionhaving the lower layer coil 30 (i.e., at a position close to the upperlayer coil 20) and (B) the magnetic fields E2 and E4 have the samedirection at a lower part of an upper layer portion having the upperlayer coil 20 (i.e., at a position close to the lower layer coil 30) andan upper part of a lower layer portion having the lower layer coil 30(i.e., at a position close to the upper layer coil 20). In such manner,a high-frequency magnetic field H is generated between the upper layercoil 20 and the lower layer coil 30 with a direction from the point P4to the point P3 as the magnetic field direction, as shown by a whitearrow in FIG. 5B. Since the electric current flowing in the upper layercoil 20 and the lower layer coil 30 is a high-frequency current, theposition where the current amplitude takes the maximum value and theposition where the current amplitude takes the minimum valuerespectively change, thereby a high-frequency magnetic field having themagnetic field direction changed accordingly on the XY plane isgenerated.

As a comparative example shown in FIG. 8 , consider a case where adirect current is passed in a structure in which a coil J20 wound by aplurality of times is provided in a substrate J10. In case of such aconfiguration, the electric current is reversed at a positionsymmetrical with respect to the coil central axis. Therefore, as shownin the figure (FIG. 8 ), a counter-clockwise magnetic field EJ1 isgenerated at the position on the left side of the drawing where theelectric current in the coil 20 flows in a direction to come up frombehind the paper surface toward the reader in each of the pluralwindings of the coil J20. Further, a clockwise magnetic field EJ2 isgenerated at the position on the right side of the drawing where theelectric current flows in a direction to sink into the paper surfaceaway from the reader. Therefore, a high-frequency magnetic field HJ inthe coil central axis direction is generated in the coil J20. In such acase, the measurement target needs to be arranged on the lateral side ofthe substrate J10, that is, on an outer side in the radial direction ofthe coil J20, which may pose a limitation regarding how close themeasurement target is positionable relative to the coil J20 due to thestructure described above. Further, if the measurement target is placeddirectly above or below the substrate J10, that is, in the axialdirection of the coil J20, though the distance to the measurement targetbecomes shorter, the external magnetic field is measurable because themagnetic sensor has no sensitivity in the axial direction.

Therefore, it can be said that it is effective to use the magnetic fieldgenerator 1 capable of making the XY plane in the magnetic fielddirection as in the present embodiment.

As described above, in the magnetic field generator 1 of the presentembodiment, the upper layer coil 20 and the lower layer coil 30 arearranged to be capable of supplying high-frequency electric current fromthe upper layer power source 40 and the lower layer power source 50,respectively. Further, the lead portion 23 of the upper layer coil 20and the lead portion 33 of the lower layer coil 30 are arranged to havethe same position when viewed from the normal direction of the substrate10. In such a configuration, a high-frequency current having a phasedifference of 180° is passed through the upper layer coil 20 and thelower layer coil 30. The length of one wavelength of the high-frequencycurrent is set to be substantially equal to the length of one loop ofthe coil portion 21 of the upper layer coil 20 and the coil portion 31of the lower layer coil 30.

In such a configuration, the direction of the magnetic field generatedon a lower layer coil 30 side of the upper layer portion of thesubstrate 10 which has the upper layer coil 20 provided therein and thedirection of the magnetic field generated on an upper layer coil 20 sideof the lower layer portion of the substrate 10 which has the lower layercoil 30 provided therein are matched. This makes it possible to generatea high-frequency magnetic field having the XY plane as the magneticfield direction at a position between the upper layer coil 20 and thelower layer coil 30.

Thus, the magnetic sensor provided with such a magnetic field generator1 is configured to have sensitivity in the axial direction of the upperlayer coil 20 and the lower layer coil 30, and the measurement targetgenerating a very small magnetic field is brought close either to animmediate/directly above or to an immediate/directly below the substrate10. Therefore, such a magnetic sensor is made more accurate.

Further, the magnetic field generator 1 of the present embodimentseparately includes the upper layer power source 40 that supplies ahigh-frequency current to the upper layer coil 20 and the lower layerpower source 50 that supplies a high-frequency current to the lowerlayer coil 30. Therefore, high-frequency currents having opposite phasesare suppliable from the upper layer power source 40 and the lower layerpower source 50 to the upper layer coil 20 and the lower layer coil 30,respectively.

Specifically, with respect to the magnetic field generator 1 of thepresent embodiment, the flow of electric current in the upper layer coil20 and the lower layer coil 30 and the generated high-frequency magneticfield were investigated by simulation. As a result, diagrams shown inFIGS. 9A to 9C and 10 were obtained.

When high-frequency currents are passed through the upper layer coil 20and the lower layer coil 30 and high-frequency currents have oppositephases with a 180° phase difference, the directions of the electriccurrent at various parts at an arbitrary timing is shown in FIGS. 9A to9C by arrows. That is, in the upper layer coil 20, the directions of theelectric current are opposite to each other at point-symmetric positionswith respect to the coil central axis. Similarly, in the lower layercoil 30, the directions of the electric current are opposite to eachother at point-symmetric positions with respect to the coil centralaxis. Further, at the same angle position with respect to the coilcentral axis, the electric currents in the upper layer coil 20 and thelower layer coil 30 flow in opposite directions. Then, as shown in FIG.9C, in the upper layer coil 20, an electric current is generated from anarbitrary position on one side opposite to the lead portion 23 withrespect to the coil central axis, and in the lower layer coil 30, theelectric current flows into any/arbitrary position on the opposite sideof the lead portion 23 with respect to the coil central axis.

Therefore, in a cross section diagram shown in FIG. 10 , the upper layercoil 20 generates a clockwise magnetic field, and the lower layer coil30 generates a counter-clockwise magnetic field. Therefore, as shown inFIG. 10 , at the position of the diamond 2, a high-frequency magneticfield pointing in a left direction of the paper surface is generatable,which shows that a high-frequency magnetic field is generatable in theXY plane.

Second Embodiment

The second embodiment is described. In the present embodiment, theconfigurations of the upper layer coil 20 and the lower layer coil 30are changed from those in the first embodiment, and the other parts arethe same as those in the first embodiment. Therefore, the descriptionfocuses on such difference.

As shown in FIGS. 11 and 12 , in the present embodiment, the upper layercoil 20 and the lower layer coil 30 provided in the magnetic fieldgenerator 1 each have a double-layer structure. That is, the upper layercoil 20 is composed of a first coil 210 and a second coil 220, and thelower layer coil 30 is composed of a third coil 310 and a fourth coil320.

The first coil 210 is configured to have a coil portion 211, a slit 212,and a lead portion 213. The lead portion 213 including the coil portion211, the slit 212, a first lead portion 213 a and a second lead portion213 b has the same configuration as the coil portion 21, the slit 22 andthe lead portion 23 described in the first embodiment. Further, thesecond coil 220 is configured to have a coil portion 221 and a slit 222and a lead portion 223. The lead portion 223 having the coil portion 221and the slit 222, a first lead portion 223 a and a second lead portion223 b has the same configuration as the coil portion 21, the slit 22 andthe lead portion 23 described in the first embodiment. However, here,the position where the slit 212 and the lead portion 213 of the firstcoil 210 are provided is different from the position where the slit 222and the lead portion 223 of the second coil 220 are provided, and theposition is shifted by 180° with respect to the coil central axis amongthe two.

Further, the upper layer power source 40 includes a first upper layerpower source 41 and a second upper layer power source 42. The firstupper layer power source 41 is connected to the first lead portion 213 ato energize the first coil 210, and the second upper layer power source42 is connected to the first lead portion 223 a to energize the secondcoil 220.

Further, a resistor 61 connecting the second lead portion 213 b to theGND and for reflection suppression is provided, and a resistor 62connecting the second lead portion 223 b to the GND and for reflectionsuppression is provided.

The third coil 310 is configured to have a coil portion 311, a slit 312,and a lead portion 313 having a first lead portion 313 a and a secondlead portion 313 b. The coil portion 311, the slit 312, and the leadportion 313 have the same configuration as the coil portion 31, the slit32, and the lead portion 33 described in the first embodiment. Further,the fourth coil 320 is configured to have a coil portion 321, a slit322, and a lead portion 323 having a first lead portion 323 a and asecond lead portion 323 b. The coil portion 321, the slit 322 and thelead portion 323 have the same configuration as the coil portion 31, theslit 32 and the lead portion 33 described in the first embodiment.However, here, the position where the slit 312 and the lead portion 313of the third coil 310 are provided is different from the position wherethe slit 322 and the lead portion 323 of the fourth coil 320 areprovided, and the position is shifted by 180° with respect to the coilcentral axis among the two.

Further, the lower layer power source 50 includes a first lower layerpower source 51 and a second lower layer power source 52. The firstlower layer power source 51 is connected to the first lead portion 313 ato energize the third coil 310, and the second lower layer power source52 is connected to the first lead portion 323 a to energize the fourthcoil 320.

Further, a resistor 71 connecting the second lead portion 313 b to theGND and for reflection suppression is provided, and a resistor 72connecting the second lead portion 323 b to the GND and for reflectionsuppression is provided.

In such a configuration, a high-frequency current is passed through thefirst coil 210 and the second coil 220 constituting the upper layer coil20 so that the electric currents at the same angle with respect to thecoil central axis are in phase. That is, with respect to the first coil210 and the second coil 220, since the positions of the lead portion 213and the lead portion 223 are shifted by 180°, the phase of thehigh-frequency current to be passed is also shifted by 180°.

Further, a high-frequency current having the same phase at the sameangle with respect to the coil central axis is also passed through thethird coil 310 and the fourth coil 320 constituting the lower layer coil30. However, for the third coil 310 and the fourth coil 320,high-frequency currents having a 180° phase difference from the firstcoil 210 and the second coil 220 are provided. That is, since thepositions of the lead portion 313 and the lead portion 323 of the thirdcoil 310 and the fourth coil 320 are also shifted by 180°, the phase ofthe high-frequency current to be passed is also shifted by 180°.Further, regarding the third coil 310, since the lead portion 313 isarranged at the same angle as the lead portion 213 of the first coil210, the high-frequency current is 180° out of phase with respect to thefirst coil 210. Similarly, with respect to the fourth coil 320, sincethe lead portion 323 is arranged at the same angle as the lead portion223 of the second coil 220, the high-frequency current is 180° out ofphase with respect to the second coil 220.

In such manner, as shown in FIG. 12 , the magnetic fields E3 and E4 inthe same direction can be generated at the same angle with respect tothe coil central axis in the first coil 210 and the second coil 220.Further, the magnetic fields E1 and E2 in opposite directions can begenerated in the third coil 310 and the fourth coil 320 at the sameangle as the magnetic fields E3 and E4 of the first coil 210 and thesecond coil 220 with respect to the coil central axis.

Therefore, even if the upper layer coil 20 and the lower layer coil 30are composed of two layers, a high-frequency magnetic field H having theXY plane as the magnetic field direction can be generated between theupper layer coil 20 and the lower layer coil 30. If the upper layer coil20 and the lower layer coil 30 are composed of two layers in suchmanner, the intensity of the magnetic field generated by the upper layercoil 20 and the lower layer coil 30 can be increased, and a strongerhigh-frequency magnetic field is generatable.

Third Embodiment

The third embodiment is described. The present embodiment is amodification of the layout of the upper layer coil 20 and the lowerlayer coil 30 in the first embodiment, and has the same configuration asthe first embodiment for the other part. Thus, the description focuseson difference therefrom.

As shown in FIGS. 13 and 14 , in the present embodiment, the formationpositions of the slit 22 and the lead portion 23 of the upper layer coil20 and the formation positions of the slit 32 and the lead portion 33 ofthe lower layer coil 30 are different. Here, the formation positions ofthe slit 22 and the lead portion 23 of the upper layer coil 20 and theformation positions of the slit 32 and the lead portion 33 of the lowerlayer coil 30 are shifted by 90° with respect to the coil central axis.Specifically, assuming that the position of the first lead portion 23 ain the upper layer coil 20 is 0° and the position of the second leadportion 23 b is 360°, the slit 32 and the lead portion 33 in the lowerlayer coil 30 are arranged at 270°.

In such a configuration, the initial phase of the high-frequency currentflowing through the upper layer coil 20 is set to 90°, and the initialphase of the high-frequency current flowing through the lower layer coil30 is set to 0°. In such manner, the phase of the high-frequency currentcan be shifted by 180° at the same angle with respect to the coilcentral axis among the upper layer coil 20 and the lower layer coil 30.

Therefore, even if the formation positions of the slit 22 and the leadportion 23 of the upper layer coil 20 and the formation positions of theslit 32 and the lead portion 33 of the lower layer coil 30 are differentangles, i.e., without having the same angle, with respect to the coilcentral axis, the same effect as the first embodiment is obtainable.

Here, the formation positions of the slit 22 and the lead portion 23 ofthe upper layer coil 20 and the formation positions of the slit 32 andthe lead portion 33 of the lower layer coil 30 are shifted by 90° withrespect to the coil central axis. However, the shift angle may be otherthan 90°, of course.

Fourth Embodiment

The fourth embodiment is described. In the present embodiment, theshapes of the upper layer coil 20 and the lower layer coil 30 arechanged with respect to the first to third embodiments, and the otherparts are the same as those in the first to third embodiments. Thus,only the different parts from the first to third embodiments aredescribed.

As shown in FIGS. 15 and 16 , in the present embodiment, the coilportion 21 of the upper layer coil 20 and the coil portion 31 of thelower layer coil 30 are not annular but square. Specifically, the coilportion 21 is formed in a rectangular shape composed of two opposingshort sides and two opposing long sides, and the slit 22 and the leadportion 23 are arranged on one of the short sides. Similarly, the coilportion 31 is formed in a rectangular shape composed of two opposingshort sides and two opposing long sides, and the slit 32 and the leadportion 33 are arranged on one of the short sides. The coil portion 21and the coil portion 31 are arranged to face each other so that theirshort sides overlap each other and their long sides overlap each other(in a plan view).

The slit 22, the lead portion 23, the slit 32, and the lead portion 33may be arranged at the same angle with respect to the coil central axisas in the first embodiment. However, in the present embodiment, they arearranged at positions shifted by 180°. In such an arrangement, ahigh-frequency current having an initial phase of 0° may be passedthrough the upper layer coil 20 and the lower layer coil 30.

In such manner, even when the coil portion 21 and the coil portion 31have a quadrangular shape, the same effect as the first embodiment isachievable if the length per loop is set to one wavelength of thehigh-frequency current flowing through them.

Further, when the coil portion 21 and the coil portion 31 have arectangular shape, by adjusting an aspect ratio, which is a ratio of avertical dimension to a horizontal dimension of the rectangular shape onthe XY plane, the magnetic field direction is controllable. When thecoil portion 21 and the coil portion 31 have a rectangular shape, theaspect ratio corresponds to a ratio of the long side to the short side.In such a configuration, a high-frequency magnetic field can begenerated weakly in the direction of an arrow E along the long side andstrongly in the direction of an arrow F along the short side. Therefore,the direction of the magnetic field can be substantially controlled inthe direction of the arrow F.

Fifth Embodiment

The fifth embodiment is described. The present embodiment is the same asthe first to fourth embodiments in that the form of the high-frequencycurrent input to the upper layer coil 20 and the lower layer coil 30 ischanged from the first to fourth embodiments. Therefore, only the partsdifferent from the first to fourth embodiments in the present embodimentare described.

As shown in FIG. 17 , in the magnetic field generator 1 of the presentembodiment, a phase adjuster 80 that adjusts the phase of thehigh-frequency current flowing through the upper layer coil 20 and aphase adjuster 90 that adjusts the phase of the high-frequency currentflowing through the lower layer coil 30 are provided. Then, thehigh-frequency current output from the upper layer power source 40 isphase-adjusted by the phase adjuster 80, and a high-frequency currenthaving the same phase is passed through both the first lead portion 23 aand the second lead portion 23 b to both ends of the coil portion 21.Similarly, the high-frequency current output from the lower layer powersource 50 is phase-adjusted by the phase adjuster 90, and ahigh-frequency current having the same phase is passed through both thefirst lead portion 33 a and the second lead portion 33 b to both ends ofthe coil portion 31.

In the magnetic field generator 1 configured in such manner, a standingwave can be generated by a high-frequency current flowing through theupper layer coil 20 and the lower layer coil 30. For example, as shownin FIGS. 17 and 18 , the upper layer coil 20 has, for an illustration ofthe phase, four points G to K, substantially at every 90° intervals withrespect to the coil central axis from one end on a first lead portion 23a side to the other end on a second lead portion 23 b side. In suchcase, for example, a high-frequency current is supplied to both ends ofthe coil portion 21 as an input I and an input II, and the phasedifference of the high-frequency current is set to 0° (i.e., no phasedifference among the inputs I and II). In such manner, as shown in FIG.19A, a standing wave having the positions of points G, I, and K as nodesand the positions of points H and J as antinodes having the maximumamplitude can be generated by a high-frequency current. In such case, itis possible to generate a high-frequency magnetic field in which themagnetic field direction alternates repeatedly between the following twodirections, i.e., in a direction from the point H to the point J and adirection from the point J to the point H.

Further, for example, when the phase difference of the high-frequencycurrents flowing from both ends of the coil portion 21 is set to 180°,as shown in FIG. 19B, a standing wave with the positions of the pointsG, I, and K as an anti-node and the positions of the points H and J as anode can be generated. In such case, it is possible to generate ahigh-frequency magnetic field in which the magnetic field directionalternates repeatedly between the following two directions, i.e., in adirection from the point G or the point K to the point I and a directionfrom the point I to the point G or the point K.

Further, though an example of the upper layer coil 20 has been describedwith reference to FIGS. 18, 19A and 19B, the same applies to the lowerlayer coil 30. Then, a standing wave having a 180° phase difference isformed respectively in the upper layer coil 20 and the lower layer coil30. In such manner, matching between the directions of the two magneticfields is achievable. That is, the direction of the magnetic fieldgenerated on a lower layer coil 30 side of the upper layer portion ofthe substrate 10 which has the upper layer coil 20 provided therein andthe direction of the magnetic field generated on an upper layer coil 20side of the lower layer portion of the substrate 10 which has the lowerlayer coil 30 provided therein are matchable. Therefore, ahigh-frequency magnetic field having the XY plane as the magnetic fielddirection can be generated.

In such manner, a standing wave can be generated by allowing ahigh-frequency current to flow from both ends of the upper layer coil 20and the lower layer coil 30. Thus, while limiting the magnetic fielddirection to a certain/specific direction(s), a high-frequency magneticfield having alternate magnetic field directions of 180° is generatableon the XY plane.

Note that the phase adjuster 80 generating high-frequency currents inputfrom both of the first lead portion 23 a and the second lead portion 23b based on one signal source of the upper layer power source 40 in thepresent disclosure may be modifiable. That is, the phase adjuster 80 notonly adjusts the phase based on one signal and divides it into twosignals, but may also adjust the phase of each signal using the twosignals and outputs the adjusted as a high-frequency current. Of course,the same applies to the phase adjuster 90.

Sixth Embodiment

The sixth embodiment is described. The present embodiment is the same asthe first to fourth embodiments in that the form of the high-frequencycurrent input to the upper layer coil 20 and the lower layer coil 30 ischanged from the first to fourth embodiments. Therefore, only the partsdifferent from the first to fourth embodiments in the present embodimentare described.

In the magnetic field generator 1 of the present embodiment, as shown inFIGS. 20A and 20B, the same configuration as that of the firstembodiment and the like is further modified, for controlling the inputdirection of the high-frequency current to the upper layer coil 20 to beswitchable, thereby allowing clockwise and counter-clockwise rotation ofthe magnetic field direction as a circularly polarized wave. Forexample, as shown in FIGS. 20A and 20B, an input change switch 100 isprovided between the upper layer coil 20 and the upper layer powersource 40 and the resistor 60, for the switching of the input end of theupper layer coil 20 which receives an input of a high-frequency current.Further, although not illustrated, the lower layer coil 30 is alsoprovided with the input change switch 100 just like the upper layer coil20, at a position between the lower layer coil 30 and the lower layerpower source 50 or the resister 70, for switching an input of thehigh-frequency current.

In such manner, it possible to control the rotation direction of themagnetic field direction on the XY plane. For example, a high-frequencycurrent is input from the first lead portion 23 a to the upper layercoil 20, and a 180° phase difference is added to the lower layer coil 30relative to the upper layer coil 20 for an input of a high-frequencycurrent from the first lead portion 33 a. In such case, as shown in FIG.20A, the direction of the magnetic field can be rotated rightward, i.e.,clockwise, from a point M toward a point L. On the contrary, ahigh-frequency current is input to the upper layer coil 20 from thesecond lead portion 23 b, and a 180° phase difference is also added tothe lower layer coil 30 relative to the upper layer coil 20 for an inputof a high-frequency current from the second lead portion 33 b. In suchcase, as shown in FIG. 20B, the direction of the magnetic field can berotated leftward, i.e., counter-clockwise, from the point L to the pointM.

In particular, in a magnetic sensor using a diamond NVC (NitrogenVacancy Center), circularly polarized waves are used for ahigh-frequency magnetic field, and by switching the direction of thecircularly polarized waves, unpaired electrons can be selectively pumpedto either of degeneracy ms=±1. In such manner, a highly sensitivemagnetic sensor with excellent minimum resolution can be realized.

Seventh Embodiment

The seventh embodiment is described. In the present embodiment, theupper layer coil 20 is changed to a resonance coil with respect to thefirst to sixth embodiments, and the other parts are the same as those inthe first to sixth embodiments. Therefore, only the parts different fromthe first to sixth embodiments are described in the present embodiment.In the following, a case where the coil portion 21 of the upper layercoil 20 and the coil portion 31 of the lower layer coil 30 respectivelyhave an annular shape as in the first embodiment is described as anexample. However, configuration may also be the one as shown in thesecond to sixth embodiments.

As shown in FIGS. 21, 22 and 23 , the upper layer coil 20 is composed ofonly the coil portion 21 and the slit 22, and a high-frequency currentis not supplied from the power source to the upper layer coil 20. Then,the high-frequency current is supplied from the power source 50 only tothe lower layer coil 30. In such a configuration, when a high-frequencycurrent is passed through the lower layer coil 30, the upper layer coil20 is magnetically coupled or field-coupled to the lower layer coil 30,and the upper layer coil 20 functions as a resonance coil to generate LCresonance. Therefore, the resonance frequency of the upper layer coil 20is adjusted to a frequency in which the length per loop of the coilportion 31 corresponds to one wavelength. That is, the frequency atwhich the electric length of the coil portion 31 becomes one wavelengthis set as the resonance frequency.

The magnetic field generator 1 having such a configuration can also beused. In such a configuration, when a high-frequency current is passedthrough the lower layer coil 30, the electric currents of the upperlayer coil 20 and the lower layer coil 30 at the same angle with respectto the coil central axis are controllable to flow in opposite directionsfrom each other based on the LC resonance. Therefore, as in the firstembodiment, a high-frequency magnetic field is generatable as to havingthe XY plane between the upper layer coil 20 and the lower layer coil 30as the magnetic field direction. Thereby, the same effect as that of thefirst embodiment is achievable.

Although one slit 22 is formed in the upper layer coil 20, it is notnecessary to form the slits 22, or a plurality of slits 22 may beformed. The number of slits 22 and the size of the gap may beappropriately set so that the resonance frequency based on the LCresonance matches the frequency in which the length per loop of the coilportion 21 is one wavelength.

Further, the present embodiment can also be applied to a configurationfor generating a standing wave of a high-frequency current as in thefifth embodiment. In such case, the configuration may include the phaseadjuster 90 that supplies high-frequency current from both ends of thecoil portion 31 of the lower layer coil 30.

Further, the present embodiment can also be applied to the configurationof the sixth embodiment. In such case, since the high-frequency currentis not directly supplied from the power source to the upper layer coil20 which is the resonance coil, a structure provided with the inputchange switch 100 may be applied to the lower layer coil 30.

As a reference, with respect to the magnetic field generator 1 of thepresent embodiment, the current flow and the generated high-frequencymagnetic field in the upper layer coil 20 and the lower layer coil 30were investigated by simulation. The simulation results shown in FIGS.24 and 25 were obtained.

The direction of the electric current in various parts of the upperlayer coil 20 and the lower layer coil 30 at an arbitrary timing when ahigh-frequency current is passed through the lower layer coil 30 isindicated by arrows in FIG. 24 . That is, in the lower layer coil 30,the direction of the electric current is opposite at point-symmetricpositions with respect to the coil central axis. Further, by passing ahigh-frequency current through the lower layer coil 30, a high-frequencycurrent also flows through the upper layer coil 20, and the direction ofthe current is opposite even in the upper layer coil 20 at a positionpoint-symmetric with respect to the coil central axis. Further, at thesame angle position with respect to the coil central axis, the electriccurrents in the upper layer coil 20 and the lower layer coil 30 flow inopposite directions. Then, as shown in FIG. 24 , the upper layer coil 20is in a state where an electric current is generated from an arbitraryplace on a slit 22 side, and the lower layer coil 30 is in a state wherean electric current flows into an arbitrary place on a lead portion 33side. Although the arrow indicating the direction of the electriccurrent is shown to protrude from the upper layer coil 20 on one side ofthe upper layer coil 20 opposite to the slit 22 with respect to the coilcentral axis, the electric current actually flows from the upper endsurface of the upper layer coil 20 to a side surface thereof, toward anupper-right corner of FIG. 24

Therefore, in the cross section shown in FIG. 25 , the upper layer coil20 generates a clockwise magnetic field, and the lower layer coil 30generates a counter-clockwise magnetic field. Therefore, as shown inFIG. 25 , it can be seen that, (a) a high-frequency magnetic field canbe generated in the left direction of the paper surface at the positionof the diamond 2, and (b) a high-frequency magnetic field can begenerated in the XY plane.

OTHER EMBODIMENTS

Although the present disclosure is described with reference to theembodiments described above, the present disclosure is not limited tosuch embodiments but may include various changes and modifications whichare within equivalent ranges. In addition, various combinations andforms, as well as other combinations and forms including only oneelement, more than that, or less than that, are also within the scopeand idea of the present disclosure.

For example, in each of the above embodiments, a structure in which theupper layer coil 20 and the lower layer coil 30 are provided in onesubstrate 10 and integrated is given as an example. However, this isonly an example, and the substrate 10 may be divided into a plurality ofsheets/layers, and may have a structure, in which an upper layer portionhaving the upper layer coil 20 and a lower layer portion having thelower layer coil 30 may separately be provided, and a dielectric filmmay be sandwiched therebetween. In such case, at least a portion of thesubstrate 10 between the upper layer coil 20 and the lower layer coil 30may be made of/filled with a dielectric material.

Further, although a case where the upper layer coil 20 and the lowerlayer coil 30 are respectively provided with two layers has beendescribed in the second embodiment, each of the coils 20, 30 may haveonly one layer or may have a plurality of layers, i.e., may have two ormore layers. The number of layers of the upper layer coil 20 and thenumber of layers of the lower layer coil 30 may be the same ordifferent. Further, even in a structure in which the upper layer coil 20and the lower layer coil 30 have one layer or a plurality of layers, asdescribed in the third embodiment, the slits and the lead portions maybe arranged at different angles with respect to the coil central axis.

Further, in the fourth embodiment, a rectangular shape is given as oneexample of a case where the coil portion 21 of the upper layer coil 20and the coil portion 31 of the lower layer coil 30 may have a polygonalshape. However, this is also only an example, and the shape of the coilportion may also be a quadrangle other than a rectangle, for example, arhombus, or may also be a polygon other than a quadrangle such as atriangle or a pentagon. Of course, the circular/ring shape may also bean elliptical shape, or each corner of the polygonal shape may berounded. In the first to third and fifth to seventh embodiments, sincethe coil portion 21 of the upper layer coil 20 and the coil portion 31of the lower layer coil 30 are formed in an annular shape, the shape ofthe coil on the XY plane has the aspect ratio of vertical/horizontaldimensions as 1:1, when assuming that one direction of the XY plane is avertical direction and another direction perpendicular to it is ahorizontal direction. However, if the coil portion 21 and the coilportion 31 have an elliptical shape, the aspect ratios can be madedifferent, and a strong high-frequency magnetic field can be generatedin a direction along one side with a smaller aspect ratio. Of course,even when the coil portion 21 and the coil portion 31 have a polygonalshape other than a rectangle, a strong high-frequency magnetic field canbe generated in a direction along one side with the smaller aspectratio, i.e., by making the aspect ratio different from 1:1.

Further, in each of the above embodiments, the case where (a) the firstconductive material constituting the upper layer coil 20 and the secondconductive material constituting the lower layer coil 30 are copper and(b) the material of the substrate 10 is an epoxy-based resin materialhas been described as an example. However, such a configuration is onlyan example, and other materials may also be used. It may be preferablethat the constituent materials of the upper layer coil 20 and the lowerlayer coil 30 are the same, but different constituent materials may alsobe used.

Further, in each of the above embodiments, the diamond 2 has beendescribed as an example of the magnetic field measuring element, but anobject other than the diamond 2 may also be used. Further, in each ofthe above embodiments, the case where the magnetic field generator 1 isapplied to a magnetic sensor that receives a fluorescence by irradiatingit with a laser beam has been described. However, it can also be appliedto the method of (a) having an electric signal by irradiating a laserbeam or (b) obtaining electrical output by inputting an electric signal.That is, it can be applied to PDMR (Photocurrent Detection MagneticResonance), EDMR (Electric Detection Magnetic Resonance) and the like.

In each of the above embodiments, the expressions “upper and lower” areused as the upper layer coil 20 and the lower layer coil 30, but it isonly shown that the coils constituting the two loop circuits areoverlapped and lined up at a predetermined distance, and it does notmean the direction of a top and bottom.

What is claimed is:
 1. A magnetic field generator comprising: an upperlayer coil composed of a first conductive material and forming a loopcircuit having a coil portion; a lower layer coil composed of a secondconductive material and forming a loop circuit having a coil portionarranged opposite to the coil portion of the upper layer coil at apredetermined distance; a substrate supporting the upper layer coil andthe lower layer coil and having a dielectric material between the upperlayer coil and the lower layer coil; a ground layer having a groundpotential arranged to sandwich the upper layer coil and the lower layercoil on one surface and an other surface of the substrate; and a lowerlayer power source that supplies a high-frequency current to the lowerlayer coil, wherein the upper layer coil is a resonance coil that ismagnetically coupled or electrically coupled to the lower layer coil, bysupplying the high-frequency current to the lower layer coil, ahigh-frequency current having a phase opposite to that of thehigh-frequency current supplied to the lower layer coil flows throughthe upper layer coil, and a length per loop of the coil portion in theupper layer coil and in the coil portion in the lower layer coil ismatched to one wavelength of the high-frequency current.
 2. The magneticfield generator of claim 1, wherein a slit is formed in the coil portionof the lower layer coil, and the high-frequency current from the powersource is supplied to one of both ends of the coil portion formed by theslit, and an input change switch is provided for switching which of theboth ends of the coil portion of the lower layer coil that receives asupply of the high-frequency current from the power source.
 3. Themagnetic field generator of claim 1, wherein a slit is formed in thecoil portion of the lower layer coil, and a phase adjuster is providedfor generating a standing wave of the high-frequency current in thelower layer coil when supplying the high frequency current from thepower source to both ends of the coil portion formed by the slit.
 4. Themagnetic field generator of claim 1, wherein a plane parallel to thecoil portion of the upper and lower layer coils and positioned betweenthe upper layer coil and the lower layer coil is designated as an XYplane with one direction called as a vertical direction and otherdirection called as a horizontal direction, and the coil portion of theupper layer coil or the lower layer coil has an aspect ratio of 1regarding dimensions along a vertical and a horizontal dimension.
 5. Themagnetic field generator of claim 1, wherein a plane parallel to thecoil portion of the upper and lower layer coils and positioned betweenthe upper layer coil and the lower layer coil is designated as an XYplane with one direction called as a vertical direction and otherdirection called as a horizontal direction, and the coil portion of theupper layer coil or the lower layer coil has an aspect ratio of otherthan 1 regarding dimensions along a vertical and a horizontal dimension.6. The magnetic field generator of claim 1, wherein a slit is formed inthe coil portion of the lower layer coil, and the high-frequency currentfrom the power source is supplied to one of both ends of the coilportion formed by the slit, and a slit is formed in the coil portion ofthe upper coil at a position opposite to a position of the slit of thecoil portion of the lower layer coil in a radial direction of the coilportion of the upper coil.